Grain-oriented 3% Si-Fe strips were plastically strained up to %. The frequency spectrum of the Barkhausen noise was measured. From a mean Barkhausen volume veffis calculated. The noise and veffare diminished after plastic deformation mainly already in the region %, where the coercive field remains still constant, veffis related to a mean irreversible susceptibility, which is mainly determined by the hysteresis loop. By measurements of the correlation of the flux changes along the specimen a mean length of the Barkhausen volumes was obtained. Its diminution mainly causes the diminution of veff. The connection of the results with changes of the domain and dislocation structure is discussed.